docs: def import_crud(app):
      '''
      Import crud module and register all model cruds which it contains
      '''
  
      try:
          app_path = import_module(app).__path__
      except (AttributeError, ImportError):
          return None
  
      try:
          imp.find_module('crud', app_path)
      except ImportError:
          return None
  
      module = import_module("%s.crud" % app)
  
      return module